Generally, since an EL element is a self-luminous type element, it is used as a backlight in a liquid crystal display, a light source in a printer head, a segment in a segment type display, a pixel in a matrix type display and others. In particular, a display in which the EL element functions as a pixel achieves a wide field angle, high contrast, an excellent visual recognition property, a low power consumption, a good shock resistance and others. As the EL elements, there are an inorganic EL element which is a thin film structure in which insulating films are interposed between an EL layer using an inorganic compound as a luminescent material and a pair of electrodes, and an organic EL element which is a laminated structure using an organic compound as a luminescent material.
FIG. 22 shows a structure of a typical luminescent panel using organic EL elements. A luminescent panel 901 is constituted by sequentially laminating an anode electrode 903, an organic EL layer 904 including a luminescent material and a cathode electrode 905 on one surface 902a of a transparent substrate 902. The organic EL layer 904 may have a three-layer structure including a hole transport layer, a luminescent layer and an electron transport layer laminated on the cathode electrode 903 in the mentioned order, a two-layer structure consisting of an electron hole transport layer and a luminescent layer from the side of the anode electrode 903 in the mentioned order, a single-layer structure consisting of a luminescent layer, or a laminated structure that transport of electrons or electron holes is interposed between appropriate layers in the former layer structures.
In the luminescent panel 901, when a forward bias voltage is applied between the anode electrode 903 and the cathode electrode 905, the electron holes are injected into the organic EL layer 904 from the anode electrode 903, and the electrons are injected into the organic EL layer 904 from the cathode electrode 905. When the electron holes and the electrons are transported into the organic EL layer 904 and the electron holes and the electrons are re-combined in the organic EL layer 904, excitons are generated, and a fluorescent material in the organic EL layer 904 is excited by the excitons whereby light is generated in the organic EL layer 904.
Generally, the luminescent panel 901 uses the anode electrode 903 as a transparent electrode, and the light is emitted toward the outside from the other surface 902b of the transparent substrate 902. At this moment, since the light emitted from the organic EL layer 904 spreads in a radial pattern, the light emitting efficiency is improved in the luminescent panel 901 by providing the light blocking effect to the cathode electrode 905.
Since the light does not have the directivity in the luminescent panel 901 and the light emitted from the organic EL layer 904 spreads in a radial pattern, a part of the light passing through the transparent substrate 902 is scattered in the transparent substrate 902, thereby reducing the light emitting efficiency from the transparent substrate 902 to the outside.
Further, when the luminescent panel 901 is used in a matrix type display, since the light emitted from the organic EL layer 904 spreads in a radial pattern, it is hard to sufficiently increase the contrast of a display screen in the front face direction.
Thus, the present invention is advantageous in increasing the light emitting efficiency of the light emission panel by a light emission element such as an organic EL element forming a laminated structure laminated on a transparent substrate and providing the directivity to light emission of a luminescent panel.